Knife sharpener

ABSTRACT

Knife sharpener comprising a pair of rolling supports providing knife blade guide surfaces of generally frusto-conical form spaced along an axis, an abrasive mounted between the supports and having blade sharpening surfaces respectively facing and making acute angles with the guide surfaces, and risers extending between the guide surfaces and the sharpening surfaces, the risers making angles with the sharpening surfaces larger than the acute angles, at least one of the guide surfaces departing from the frusto-conical form at protuberances spaced angularly from each other with respect to the axis, the protuberances merging into the frusto-conical form.

[22] Filed:

United States Patent Hayes KNIFE SHARPENER [72] Inventor: Robert M. Hayes, 24 Webster Ave.,

Somerville, Mass. 02141 Feb. 11, 1911 21 Appl. No.: 114,578

[52] US. Cl. ..51/210 [51] Int. Cl, ..B24b 3/54 [58] Field of -Search....5 l/l02, 128, 208, 210, 170 T, 51/173 [56] References Cited UNITED STATES PATENTS 3,238,673 3/l966 Thompson ..51/210 X 2,498,018 2/1950 Thompson ..51/210 [15] 3,691,700 51 Sept. 19, 1972 Primary Examiner-Donald G. Kelly Attorney-John Noel Williams [5 7] ABSTRACT Knife sharpener comprising a pair of rolling supports providing knife blade guide surfaces of generally frusto-conical form spaced along an axis, an abrasive mounted between the supports and having blade sharpening surfaces respectively facing and making acute angles with the guide surfaces, and risers extending between the guide surfaces and the sharpening surfaces, the risers making angles with the sharpening surfaces larger than the acute angles, at least one of the guide surfaces departing from the frusto-conical form at protuberances spaced angularly from each other with respect to the axis, the protuberances merging into the frusto-conical form.

5 Claims, 3 Drawing Figures KNIFE SHARPENER This invention relates to knife sharpeners of the type in which an abrasive is mounted between a pair of rolling supports.

The primary object of the invention is to adapt such rolling sharpeners for improved sharpening of serrated blades.

In general the invention features a knife sharpener comprising a pair of rolling supports providing knife blade guide surfaces of generally frusto-conical form spaced along an axis, an abrasive mounted between the supports and having blade sharpening surfaces respectively facing and making acute angles with the guide surfaces, and risers extending between the guide surfaces and the sharpening surfaces, the risers making angles with the sharpening surfaces larger than the acute angles, at least one of the guide surfaces departing from the frusto-conical form at protuberances spaced angularly from each other with respect to the axis, the protuberances merging into the frusto-conical. In preferred embodiments the guide surface has four protuberances spaced 90 apart as shown, or three spaced 120 apart, not shown; the departure of each protuberance from the frusto-conical form varies directly with distance from the axis; each protuberance has a maximum angular extent with respect to the axis of no more than half its maximum distance from the axis; and the protuberances merge into the frusto-conical form short of the riser.

Other objects, features, and advantages will appear from the following description of a preferred embodiment taken together with the attached drawings in which:

FIG. 1 is a perspective view of a sharpener embodying the invention;

FIG. 2 is a side elevation, partly broken away, of the sharpener of FIG. 1; and

FIG. 3 is a plan view of a blade guide face.

Referring to the drawings, the sharpener has a pair of rubber tired plastic wheels l2, 14 mounted at opposite ends of an axle of square cross-section. A metal blade guide face 16, 18 covers the inner face of each wheel. Each guide face has guide surface 20 of frustoconical form except for four protuberances 22, and a 1 central riser 24. Between the risers, on axle l0, fits abrasive wheel 26 having recesses 28, 30 to allow the risers 24 to extend slightly past annular sharpening surfaces 32, 34. Guide surfaces 20 make an angle of 20 with surfaces 32, 34 (between protuberances 22). Risers 24 make an angle of 45 with surfaces 32, 34.

Each protuberance 22 is highest (about three-thirty seconds inch above the frusto-conical form of surface 20) at the outer rim of face l6, l8, and tapers down to merge with the frusto-conical form at 36, just short of riser 24. The four protuberances are spaced apart with respect to axis 38 of the 1.5 inch diameter sharpener, and the maximum angular extent of each is three-eighths inch. In general, each protuberance has a maximum angular extent no more than half its maximum distance from the axis.

In operation, a serrated knife blade 40 is placed with its flat side against a guide face 16 or 18, its beveled edge-defining surface against sharpening surface 32 or 34. As the knife is drawn back and forth the sharpener rolls, and protuberances 22 cause the knit to rock left and rrgh t about its cutting edge as well as a out a transverse axis 42. As a result, the comers of abrasive wheel 26 enter the curves of the blade serrations, so that the entire blade is thoroughly sharpened.

Other embodiments are within the following claim s.

What is claimed is:

1. A knife sharpener, comprising a pair of rolling supports providing knife blade guide surfaces of generally frusto-conical form spaced along an axis,

an abrasive member mounted between said supports and having blade sharpening surfaces respectively facing and making acute angles with said guide surfaces, and

risers extending between said guide surfaces and said sharpening surfaces, said risers making angles with said sharpening surfaces larger than said acute angles,

at least one of said guide surfaces departing from said frusto-conical form at protuberances spaced angularly from each other with respect to said axis, said protuberances merging into said frusto-conical form.

2. The sharpener of claim 1 wherein said one guide surface has three or four said protuberances spaced or 90 apart, respectively.

3. The sharpener of claim 1 wherein the departure of each said protuberance from said frusto-conical form varies directly with distance from said axis.

4. The sharpener of claim 1 wherein each said protuberance has a maximum angular extent with respect to said axis of no more than half its maximum distance from said axis.

5. The sharpener of claim 1 wherein said protuberances merge into said frusto-conical form short of said riser. 

1. A knife sharpener, comprising a pair of rolling supports providing knife blade guide surfaces of generally frusto-conical form spaced along an axis, an abrasive member mounted between said supports and having blade sharpening surfaces respectively facing and making acute angles with said guide surfaces, and risers extending between said guide surfaces and said sharpening surfaces, said risers making angles with said sharpening surfaces larger than said acute angles, at least one of said guide surfaces departing from said frustoconical form at protuberances spaced angularly from each other with respect to said axis, said protuberances merging into said frusto-conical form.
 2. The sharpener of claim 1 wherein said one guide surface has three or four said protuberances spaced 120* or 90* apart, respectively.
 3. The sharpener of claim 1 wherein the departure of each said protuberance from said frusto-conical form varies directly with distance from said axis.
 4. The sharpener of claim 1 wherein each said protuberance has a maximum angular extent with respect to said axis of no more than half its maximum distance from said axis.
 5. The sharpener of claim 1 wherein said protuberances merge into said frusto-conical form short of said riser. 